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There were countless billions of dimensions, some of them incomprehensibly different to N-Space. Beings from these distant dimensions obeyed very different laws of physics and were (presumably) forbidden to cross into other dimensions. Nobody No-One came from a reality 45 billion dimensions away from N-Space and was composed of language and communication instead of matter and energy. (AUDIO: The Word Lord)

Time was often considered by humans to be the "fourth dimension" (TV: An Unearthly Child) and Vicki Pallister later elaborated that time, even though a dimension in itself, had dimensions of its own. The First Doctor even stated, in their adventure at the time, that he did not understand "this" fourth dimension. (TV: The Space Museum) Different universes possessed different time dimensions. Time moved faster in Kapron's universe, requiring metabolisms to be altered so as to prevent rapid aging when travelling to it from N-space. (AUDIO: The Macros)

According to the Twelfth Doctor, the Boneless were "from a universe with only two dimensions", although the Doctor also described them as "creatures from another dimension" and mentioned a way of sending them "back to their own dimension". People in N-Space, where three dimensions were required for life to survive there, had theorised such a universe's existence, but according to the Doctor, "no-one could go there and prove its existence without a heck of a diet". (TV: Flatline)

When the universe was created, dimensions started to solidify out of the primal chaos [...] And in the aftermath of Event Zero, eleven dimensions did fight for existence. Five were triumphant - together they did become the three dimensions of space, and the two dimensions of time through which we travel. But the remaining six dimensions did still exist: although beaten, although denied their dominance, they curled and curdled amongst themselves to become a six-fold universe, separate yet conjoined.The Quantum Archangel

According to one account, a TARDIS' interior existed as a separate dimension from the rest of the universe. This meant the interior didn't exist, creating temporal grace. (TV: The Hand of Fear) Another account described TARDISes as being a part of the universe; the Tenth Doctor said that his TARDIS was "the last TARDIS in the universe". (TV: Rise of the Cybermen) According to another account, the Eleventh Doctor said that the Doctor telling Mels that the TARDIS existed in a state of temporal grace was "a clever lie" to ensure that Mels didn't fire her gun. (TV: Let's Kill Hitler) Nonetheless, the Eleventh Doctor also described the huge room inside the TARDIS which was surrounded by a tiny exterior as "basically another dimension". (TV: The Vampires of Venice) The external dimensions of the Doctor's TARDIS were leeched by the Boneless, making its exterior shell smaller but keeping the interior the same size. (TV: Flatline)

The Mavora existed in only the first two dimensions, and thus they were a completely flat shape and could slide between the atoms of the universe. (COMIC: The Broken Man)

The 2Dis was able to restore three dimensions to small objects the Boneless had flattened into two dimensions and reverse the process. After the Boneless took on a 3D form in N-Space, they had the ability to "restore" dimensions as well. (TV: Flatline)